The present invention relates to an electric vehicle in which the same shaft is driven by two or more electric motors.
Electric vehicles are known in which the same shaft is driven by two or more motors. For example, Laid-open Japanese Patent Application No. 2004-135371 discloses an electric vehicle of a construction wherein the same shaft is driven by the drive sources of two independent systems, and a technique is disclosed whereby, if abnormality occurs with one of these systems, by regenerating part of the output of the normal drive source with the drive system in which the abnormality occurred, and supplying the regenerated power to an auxiliary machine of the system in which abnormality occurred, continued running can be achieved.
In this way, by providing two or more motors in the electric vehicle, even when abnormality occurs in one of the motors, running can be achieved using the other motor.
However, if the output shafts of the motors are engaged with the same drive shaft without interposition of a clutch, discontinuance of power supply causes a non-drive condition to be produced in respect of the motor where abnormality occurred, with the result that, if running is continued with the motor that is not abnormal, a counter electromotive voltage is generated in the motor in the non-drive condition due to the rotation of the drive shaft: there was therefore a risk of a fault being produced in a circuit component such as an inverter if the counter electromotive voltage produced by high-speed running should exceed the withstand voltage of this circuit component.